The present invention is generally concerned with postage meters and mailing machines, and more particularly with improvements therein including apparatus for driving a postage meter drum.
In U.S. Pat. No. 2,934,009 issued Apr. 26, 1960 to Bach, et al. and assigned to the assignee of the present invention there is described a postage meter which includes a drive mechanism connected by means of a drive train to a postage meter drum. The drive mechanism includes a single revolution clutch for rotating the drum from a home position and into engagement with a letter fed to the drum. The drum prints a postage value on the letter while feeding the same downstream beneath the drum as the drum returns to the home position. Each revolution of the single revolution clutch and thus the drum, is initiated by the letter engaging a trip lever to release the helical spring of the single revolution clutch. The velocity versus time profile of the peripherary of a drum driven by the clutch approximates a trapezoidal configuration, having acceleration, constant velocity and deceleration portions, fixed by the particular clutch and drive train used in the application. This being the case, the throughput rate of any mailing machine associated with the meter is dictated by the cycling speed of the postage meter rather than by the speed with which the individual mailpieces are fed to the postage meter. Further, although the single revolution clutch structure has served as the workhorse of the industry for many years it has long been recognized that it is a complex mechanism which is relatively expensive to construct and maintain, does not precisely follow the ideal trapezoidal velocity vs. time motion profile which is preferred for drum motion, tends to be unreliable in high volume applications, and is noisy and thus irritating to customers.
Accordingly, an object of the invention is to replace the postage meter drum drive mechanism of the prior art with the combination of a D.C. motor and a computer, and program the computer for causing the D.C. motor to drive the drum in accordance with an ideal trapezoidal-shaped velocity versus time profile which is a function of the input velocity of a mailpiece.
As disclosed in U.S. Pat. No. 4,287,825 issued Sept. 8, 1981 to Eckert et al and assigned to the assignee of the present invention, the postage meter's drum has mounted therein conventional postage value changing apparatus, including a plurality of print wheels, each of which is provided with a plurality of digit or print elements. In addition, the postage meter drum's drive shaft has slidably mounted therein a plurality of racks which are disposed on a one-for-one basis in engagement with the print wheels. In addition, there is disclosed the provision of a postage value selection mechanism which is coupled to the drum drive shaft. The selection mechanism includes a first stepper motor and an associated gear train for selecting any one of the racks of the postage value changing apparatus and a second stepper motor and associated gear train for actuating the selected rack. The rack selection stepper motor, which is known in the art as a bank selection motor, is conventionally energized for selecting the appropriate rack to select the appropriate print wheel to be rotated and the rack actuating stepper motor, which is known in the art as a digit section motor, is conventionally energized for actuating the selected rack to rotate the selected print wheel for selecting the print element to be printed. Assuming the provision of a D.C. motor for driving the drum under the control of a computer, the drum may be selectively indexed by means of the D.C. motor for rack selection purposes; as a consequence of which the rack selection stepper motor and its associated gear train may be eliminated and the gear train associated with the digit selection stepper motor may be simplified to include a single rack actuating gear.
Accordingly, another object of the invention is to provide postage value selection means including a D.C. motor coupled to a postage meter drum and controlled by a computer; and
Another object is to provide a postage meter, including a rotary postage printing drum, with a D.C. motor controlled by a computer, wherein the computer is programmed for controlling the drum for postage value selection purposes and for postage printing purposes.